Full Description

The material that fouls reverse osmosis membranes is diverse, and is composed ofinorganic particles (precipitated metal oxides, colloids, etc.), natural organicmatter, and bacterial/fungal/algal/protozoan cells. Membrane fouling can becontrolled by a variety of methods. For example, pretreatment of the feedwater toremove particulate matter and ions is often prescribed based upon feedwaterquality. This pretreatment can include both chemical and physical processes suchas softening, ion exchange, granular activated carbon, and media filtration.Regular cleaning of the membranes is another way to control fouling. The cleaningprocess may include application of chemicals, including surfactants, oxidizingagents or biocides, to the membrane. Finally, use of special membranes thatresist fouling with modified surfaces or membranes that can tolerate chemicaltreatments may be implemented. These methods will often control fouling for aperiod of time if applied correctly. However, long term operation will provideconditions where the membrane surfaces become altered as a result of the foulinglayers, resulting in a decrease in the ability of the membrane to resist foulingand its ability to be cleaned. Part of this inability to be cleaned can beattributed to growth of bacteria as biofilms on the surface. Biofilms arenotoriously difficult to disinfect and remove from surfaces. The authors propose toreduce membrane fouling by pretreating feed water using biological reactors toremove the organic nutrients that support formation of fouling biofilms. The goalof this research was to determine if biological pretreatment can reduce foulingin membrane systems. Several objectives were set forth to test the feasibility ofutilizing biological pretreatment as a membrane pretreatment step: determine ifbiological pretreatment using biological activated BAC carbon (BAC) and ironoxide coated sand (IOCS) as support media will reduce downstream fouling;determine if chlorination as an oxidation step for feed water will reducedownstream fouling both by itself and in combination with biologicalpretreatment; determine if microfiltration of feed water will reduce downstreamfouling both by itself and in combination with biological pretreatment; and,develop evaluation methods for the first three objectives by developing andtesting assays. Includes 19 references.

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Edition: Vol. - No. Published: 05/01/2001 Number of Pages: 6File Size: 1 file , 150 KB